The Standard Railroad Company plans to run a line through Wild Horse Valley, and this is known by Charlie Doan, who seeks to buy up all the land in the valley in order to make huge profits by reselling it to the railroad. Ranchers are forced to sell through fear of the "Night Riders", a group of henchmen hired by Doan. He has repeatedly tried to buy the Running M Ranch owned by Ruth Williams and her seven-year-old brother Dickie, but she refuses to sell. Roving cowhands Jack Benton and his pals Bill, Chuck and Mopey learn from Ruth about Doan's intimidating efforts to buy her ranch, and they hire on to help her with the wild horse roundup. Henchmen Steve and Pete burn the Running M's barn. Doan learns that Jack has bought an option on the Jim Green ranch and uses this information to turn Ruth against Jack. The latter tells Doan that he is a special investigator for the railroad and empowered to make property purchases for the right-of-way in his own name. Appearing to turn against Ruth and his employer, Jack makes a deal with Doan to acquire Ruth's property. But Jack has a different plan in mind that will put an end to Doan and his Night Riders.